类声明v/s构造函数内部初始化对象的区别

问题描述

我正在为我的对象进行对象初始化和构造函数初始化，但是无法准确回答我的问题.这里的Case1和Case2有什么区别?

I was going through object initialization and constructor initialization for my object, but couldn't get exact reply to my question.What is the difference between Case1 and Case2 here;

案例1:

namespace ConsoleApplication2
{
    class MyBuilder
    {
        private MySynchronizer m_synchronizer = new MySynchronizer();

        public MyBuilder()
        {

        }

        public void ProcessRecord(int recordNumber)
        {
            m_synchronizer.Process(recordNumber);
        }
    }
}

第二种情况:

namespace ConsoleApplication2
{
    class MyBuilder
    {
        private MySynchronizer m_synchronizer;

        public MyBuilder()
        {
          m_synchronizer = new MySynchronizer();

        }

        public void ProcessRecord(int recordNumber)
        {
            m_synchronizer.Process(recordNumber);
        }
    }
}

这是示例代码，显示了我如何调用Builder类；

This is sample code to show how I am calling my Builder class;

 class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Press any key to stop");
            MyBuilder builder = new MyBuilder();
            builder.ProcessRecord(2);
        }
    }

[对不起，如果我不能正确地改写问题，在这种情况下，任何人都可以提供指向其他SO文章的链接]

[Sorry, if I could not have rephrase the question properly, in which case anyone can provide the link to other SO article]

推荐答案

这里的区别是确实细微，只能在IL中轻松理解:

The difference here is really subtle, and can only easily be appreciated in IL:

class MyBuilder1
{
    private MySynchronizer m_synchronizer = new MySynchronizer();

    public MyBuilder1()
    {

    }
}

为我们提供了构造函数:

gives us the constructor:

.method public hidebysig specialname rtspecialname
    instance void .ctor () cil managed
{
    // Method begins at RVA 0x2050
    // Code size 18 (0x12)
    .maxstack 8

    IL_0000: ldarg.0
    IL_0001: newobj instance void MySynchronizer::.ctor()
    IL_0006: stfld class MySynchronizer MyBuilder1::m_synchronizer
    IL_000b: ldarg.0
    IL_000c: call instance void [mscorlib]System.Object::.ctor()
    IL_0011: ret
} // end of method MyBuilder1::.ctor

位置-

class MyBuilder2
{
    private MySynchronizer m_synchronizer;

    public MyBuilder2()
    {
      m_synchronizer = new MySynchronizer();

    }
}

给予我们

// Methods
.method public hidebysig specialname rtspecialname
    instance void .ctor () cil managed
{
    // Method begins at RVA 0x2063
    // Code size 18 (0x12)
    .maxstack 8

    IL_0000: ldarg.0
    IL_0001: call instance void [mscorlib]System.Object::.ctor()
    IL_0006: ldarg.0
    IL_0007: newobj instance void MySynchronizer::.ctor()
    IL_000c: stfld class MySynchronizer MyBuilder2::m_synchronizer
    IL_0011: ret
} // end of method MyBuilder2::.ctor

区别只是订购之一:

• 字段初始值设定项( MyBuilder1 )发生在基本类型构造函数调用之前( object 是这里的基础； 调用实例无效[mscorlib] System.Object ::.ctor()是基本构造函数调用)
• 构造函数发生在 基本类型构造函数调用之后

• field initializers (MyBuilder1) happen before the base-type constructor call (object is the base here; call instance void [mscorlib]System.Object::.ctor() is the base-constructor call)
• constructors happen after the base-type constructor call

在大多数情况下，这无关紧要.除非您的基本构造函数调用派生类型将覆盖的虚拟方法:否则，该字段在覆盖方法中是否具有值将在两者之间有所不同.

In most cases, this won't matter. Unless your base-constructor invokes a virtual method that the derived type overrides: then whether or not the field has a value in the overridden method will be different between the two.

这篇关于类声明v/s构造函数内部初始化对象的区别的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！